1. Field of the Invention
The present invention relates to a lock assembly, and more particularly to a lock assembly for a bicycle or the like to ensure smooth linear movement of the latch bolt.
2. Description of Related Art
With reference to FIGS. 8 and 9, a conventional lock assembly comprises a casing (60), a cylinder assembly (50) and a shank (70). The cylinder assembly (50) is mounted inside the casing (60). The shank (70) is partially inserted into the casing (60) and is held in the casing (60) by the cylinder assembly (50).
The casing (60) is cylindrical and has a distal end (not numbered), a cylinder chamber (61) and a shank chamber (62). The cylinder chamber (61) is formed longitudinally in the distal end of the casing (60) and has an open outside end (not numbered), an inside end (not numbered) and a bolt hole (63). The bolt hole (63) is formed through the inside end of the cylinder chamber (61). The shank chamber (62) is formed diametrically in the casing (60) near the inside end of the cylinder chamber (61), communicates with the bolt hole (63) in the cylinder chamber (61) and has an open outside end (not numbered) and an inside end (not numbered).
The cylinder assembly (50) is mounted securely inside the cylinder chamber (61) and has a cylinder (51), a plug (not shown), a bolt driver (52), a bolt (53) and a spring (55). The cylinder (51) is mounted in the open outside end of the cylinder chamber (61). The plug has an inside end (not shown), an outside end (not shown) and a keyhole (not shown) and is rotatably mounted inside the cylinder (51). The keyhole is formed axially through the outside end of the plug. The bolt driver (52) is cylindrical, is attached to the inside end of the plug and has a push pin (521) formed radially through and extending from the bolt driver (52). The bolt (53) is cylindrical and has an internal cavity (not numbered), an outer surface (not numbered), an open end (not numbered), a closed end (not numbered), a flange (531) and a spiral groove (54). The internal cavity is formed longitudinally through the open end of the bolt (53). The flange (531) is formed on the outer surface at the open end of the bolt (53) and extends radially from the outer surface. The spiral groove (54) is formed through the outer surface of the bolt (53) from the open end and communicates with the internal cavity. The internal cavity and open end of the bolt (53) are mounted slidably on the bolt driver (52) with the push pin (521) slidably mounted in the spiral groove (54). The spring (55) is mounted around the bolt (53) between the flange (531) and the inside end of the cylinder chamber (61) to provide a restitution force to the bolt (53). When the lock assembly is unlocked, the closed end of the bolt (53) is positioned in the bolt hole (63), and the open end and the flange (531) are held against the inside end of the plug by the spring (55).
The shank (70) is cylindrical and has a distal end, a head (not numbered), a radial recess (71) and a neck (not numbered). The head is formed on the distal end of the shank (70). The neck forms the radial recess (71) around the shank (70). When the shank (70) is inserted into the shank chamber (62) through the open end of the shank chamber (62), the radial recess (71) aligns with the bolt hole (63).
The lock assembly is operated by inserting the shank (70) fully into the shank chamber (62), inserting a key (80) into the keyhole and rotating the key to rotate the plug, which rotates the bolt driver (52) and the push pin (521) about 90°. When the push pin (521) rotates and moves in the spiral groove (54), a force is generated to push closed end of the bolt (53) into the shank chamber (62) and the radial recess (71) around the shank (70). Thereby, the lock assembly is locked.
However, friction between the push pin (521) and the spiral groove (54) causes the push pin (521) and the spiral groove (54) to wear. Specifically, the push pin (521) wears down and eventually shears off causing the lock assembly to fail. Uneven wear of the spiral groove (54) causes the lock assembly to operate erratically. Therefore, the conventional lock assembly is neither reliable nor durable and these problems can lead to considerable frustration where a user is unable to unlock the locked item.
The present invention has arisen to mitigate or obviate the disadvantages of the conventional lock assembly.